Concrete reinforcing bar



y 1, 1945- c. A. MENZEL I L 2,374,827

GONG TE INF R I v I Filed Sept. 20, 1941 fizaezz/ar:

Patented May 1, 1945 UNITED STATES PATENT OFFICE CONCRETE REINFORCING BAR Carl A. Menzel, Homewood, Ill.

Application September 20, 1941, Serial No. 411,705

25 Claims.

For as long as reinforced concrete has been known, eil'orts have been made to improve the bond between the metal reinforcing bars and the concrete in which they were embedded. The almost innumerable forms of bars which have been made or proposed heretofore bear mute testimony of the general recognition that the bond was not all that was desired and of the frequent attempts through the years to provide better bond. As a result of research extending over a period of years, it has become apparent to me that bars which utilized one principle better than others did so at the sacrifice of other principles, and that there were some principles that were not fully utilized by any of the commercial bars, perhaps not being recognized by those who devised them. I have also discovered, and verified by research, that at least one feature thought to be objectionable is in fact desirable.

In reinforced concrete a comparatively small volume of steel is embedded in a large volume of concrete. Since steel is a much stronger and tougher material than concrete, it is possible for a small volume of properly embedded steel to carry a large proportion of the load imposed on the concrete encasing the steel. The transfer of load or stress from the concrete to thesteel is made possible by the resistance established between the concrete and the surface of theembedded steel bar. The higher this resistance to relative motion or slippage under stress, the more effective will be the desired interaction between the concrete and the steel. This resistanc to slippage has been called bond or bond resistance. I

Without any bond resistance the embedded steel would be practically useless. With adequate bond the primary requirement for proper interaction is met and both steel and concrete can be stressed as intended by the designer with economy and safety.

One desirable feature in reinforcing bars is to have the anchoring projections or ribs which interlock with the concrete extend generally transversely or circumferentially of the bar since thepull on the bar is longitudinal of the bar. Many bars have had their projections disposed perpendicularly to the axis of the bar. From the standpoint of anchorage with the minimum of metal in a projection, this might seem to be ideal but the metal in the projections is wasted from the standpoint of tensile strength of the bar, since the bar is weaker between the projections than at the position of the projections.

Some bars have gone to the other extreme and provided projections which had a steep longitudinal pitch or even extended parallel to the axis of the 'bar and were so disposed as to provide a bar of uniform cross-sectional area throughout its length.

Prior to this invention it has been generally assumed that the faces of the projections must be quite steep so that the pull on the bar will be so nearly perpendicular to these faces that the faces will not tend to form wedge-like surfaces which will split the concrete. The faces have generally been fiat and as steep as they could conveniently be made and with a fillet so small as to be-negligible. One publicationhas indicated that the face should make an angle of at least with the axis of the bar. A feature of the present invention lies in determining that this theory is erroneous and that a fillet of large radius gives as good anchorage as the flat faces with insignificant fillets heretofore provided. Apparently with a fillet of large radius the cement makes so much better contact with the metal that it more than oflsets any splitting tendency it might otherwise have. As a matter of fact, if the outer portion of the fillet is fairly steep, it is probable that it will always provide anchorage before theinner, less steep portion of the fillet exerts any very great splitting force. In any event, it is more important to prevent or minimize slipp e of the bar in the concrete than to consider the prevention of splitting as an end in itself, because, until the bar slips, it cannot split the concrete; and, if it slips excessively, the structure will fail whether splitting occurs or not.

The provision of large fillets in accordance with this invention aids in providing other desirable features. Without the large fillets it is diflicult to form the projections close together. When they are not formed close together, they must, in order to provide a uniform cross section satisfactorily, have a very steep pitch, and this detracts from the anchorage provided. Furthermore, the desirability of the close spacing of the generally transverse projections has probably never been adequately appreciated heretofore. The close spacing of the projectionsnot only provides more anchorage surface and a large number of interlocks but it also provides a better balance between the bearing or anchorage area of the projections and the shearing resistance available in the concrete. Furthermore, a large number of projections greatly decreases the effect of settling of the concrete. In the case of a vertically disposed bar, if the concrete settles between projections, it is obvious that, if the projections are only as far apart, the distance that the'concrete settles away from an upper projection will be not more than of that which it would be otherwise. Furthermore, a minute spacing of the concrete from the projection may be harmless while a slightly greater spacing would be very harmful. It is also possible that close spacing of the projections, together with the large radius fillets which facilitate good contact between the cement and the metal, will result in retaining the concrete in place by adhesion in spite of settling in the main body of the concrete.

There has also been an inadequate appreciation of the importance of having the projections extend around substantially the entire circumference of the bar. The ideal would be to have it extend all the way around the bar, but, for ease of rolling, it is preferred to provide a narrow longitudinal rib'along each side of the bar where the rolls approximately meet. In the past the practice has been to make this rib quite wide, the small percentage of area of the projections thus lost seeming relatively insignificant. However, in the case of a horizontally disposed bar with the longitudinal ribs at the sides of the bar instead of top and bottom, a small percentage loss of area in the transverse projections, together with a settling of the concrete away from the transverse projections along the lower portion of the bar, may result in a surprisingly high percentage of loss of bearing area. According to the present invention, therefore, the longitudinal ribs are kept quite narrow.

Although the ideal bar including all of the features discussed is the preferred form of the invention, it is of course apparent that less perfect use of the invention could be made without utilizing all of the features mentioned.

Additional objects and advantages will be apparent from the following description and from the drawing, in which:

Figs. 1 and 2 are approximate side and end views respectively of a bar chosen for illustration of the preferred form of the invention.

Fig. 3 is a development of the surface of the bar shown in Figs. 1 and 2.

Fig. 4 is a view corresponding to Fig. 3 but showing the form the bar would take if its two forming rollers were slightly offset from one 7 another.

Fig. 5 is a vertical sectional view showing the effect of settling of concrete with respect to a horizontal reinforcing bar in fixed position.

Fig. 6 is a transverse sectional view illustrating the comparatively small amount of bearing area which the lower transverse rib presents. to the settled concrete if a wide longitudinal rib is used. For the sake of clarity, Fig. 6 avoids having a helical rib intersect the sectional plane, as if the upper and lower halves were taken on separate diagonal planes between the ribs.

Fig. '7 is a view corresponding to Fig. 6 but showing the increased bearing area when a narrow longitudinal rib is used. 7 v

Fig. 8 is a vertical sectional view showing the effect of settling with respect to a vertically disposed reinforcing bar in which the trans verse ribs are far apart.

Fig. 9 is a corresponding view illustrating the negligible effect of settling on a bar having closely spaced transverse ribs.

Fig. 10 is an enlarged approximation of the longitudinal sectional view through the structure of Fig. 1 showing particularly a preferred shape for the transverse ribs.

A preferred form of'the invention has been chosen for illustration and description, in compliance with Section 4888 of the Revised Statutes, but persons skilled in the art will readily perceive other means for accomplishing the same results, and the claims are thereforeto be construed as broadly as possible, consistent with the prior. art.

As seen from Fig. 1, the bar comprises a body portion H with helically disposed ribs or projections l2 formed thereon and longitudinal ribs l3 formed thereon at opposite sides thereof. The bar is preferably manufactured by deforming a smooth-surface bar to the shape shown, the deformation being accomplished by a rolling process.

It is very desirable that the bar be of uniform cross section throughout its length. This could of course be accomplished by providing one helical rib extending continuously fromlend to end.

However, if the rolls rolling the upper and lower halves of the bar should become angularly offset with respect to one another so that the helix was not continuous, there would be some points where a transverse section through the bar would out two portions of the helix and others where such a section would not cut any portion of the helix, and the cross section therefore would not be uniform. For this reason it is preferred that each half of the bar be of uniform cross section so that offsetting of the rib on one portion with respect to those on the other will make no difference. As shown best in Fig. 3, which is the development of the surface of the bar shown in Fig. 1, this is preferably accomplished by providing a double helix for the bar as a whole so that on each half of the bar the rib extends continuously along the whole length. Thus, referring to the upper half, one rib terminates on the sectional line AA whilethe other begins on said line, and the same thing is true of the lower half. In Fig. 4 the effect is seen if the two halves are offset with respect to one another, the section lines 3-H and (3-0 cutting through different parts of the ribs on the upper half and lower half, but in each instance cutting just one helical rib orthe equivalent. The helix on each half between the longitudinal ribs should be the development of a single helix, the point d, e being in the same perpendicular plane. Of course, slight departures from the ideal will still utilize the invention though imperfectly. If there is a little excess at the ends of the ribs due to the fillets, this is insignificant, the amount of metal being small, and there being no planes weaker than the ordinary planes-merely a few that are a little stronger.

It will be observed that the ribs l3 are quite thin; preferably they are made as thin as conventional rolling practice will permit, since their value as far as anchorage is concerned is very slight and since they decrease the available P anchorage area on the ribs I2.

The surprising results from the use of a thin longitudinal rib l3 in place of a wide longitudinal rib of the prior art is illustrated in Figs. 5 to '7. Fig. 5 illustrates a section of reinforced concrete in which the concrete has settled somewhat so that it has dropped away from the bottom half of the bar a distance approximately equal to the height of the ribs [2. As seen in Fig. 5, the ribs l2 do not interlock with the concrete at the bottom of the bar. In Fig. 6 a cross secconcrete and the lower half of the ribs I2 is provided at the area II. In Fig. 7 a corresponding development of the present invention was the dc termination that this fiat side is not necessary.

p In fact, in the preferred form of the invention.

section using the bar of Figs. 1 and 2 with a nar- I row longitudinal rib .II makes available a considerably larger bearing area ll. Reducing the angular width of each longitudinal rib from about 47, representative of some prior art, to 12 typical of the range now preferred, provides an increase in available total bearing length of the transversely extending ribs from 74% of the circumference of the bar to 93% of the circumference. In terms oi percentage of the original bearing surface, this is an increase of over 25%. However, in terms of' the effective bearing area, in comparison with the bearing area eflective along the lower half of the-transverse ribs after sagging, in the situation illustrated in Figs. 6 and 7 the increase is much more startling and is represented by a comparison of the area I! with the area It. This increase appe rs to be in the neighborhood of 85%. The total effective bearing-area with the bar of this invention, as represented by Fig. 7, is about 38% greater than the total effective bearing area of the prior art, represented by Fig. 6. It should, be borne in mind that the shear resistance of the concrete is increased a corresponding amount, the shear resistance being the resistance of the concrete projecting between the ribs to being sheared off by the pressure exerted by the bearing area of the rib. The increase in circumferential extent of the rib increases the circumferential extent of the corresponding concrete portion which must be sheared oil.

The foregoing discusion has ignored the question of the spacing of the ribs. According to the present invention, the ribs are spaced much closer together than has been the commercial practice heretofore with respect to transversely extending ribs. The close spacing of the ribs has several advantages. One of them is in connection with the desirability of having the upper and lower halves of the bar, as rolled, each of uniform cross section throughout its length. In obtaining this end it is only by spacing the ribs quite close together that they can be maintained in a disposition which is quite close to a transverse or circumferential disposition. In other words, the close spacing of the ribs permits their having a relatively small angular departure from the theoretically desirable disposition which would be perpendicular to the axis of the rod. Referring to Fig. 4, it is evident that if the ribs were twice as far apart they would have to have twice the pitch shown in order to provide uniform cross section throughout the length of each half of the bar.

Heretofore it has not been considered commercially practical to deform bars to provide closely spaced ribs extending generally transversely. According to the present invention, however, the commercial dimculties are largely removed by providing fillets of large radius connecting the ribs with the bar, as seen bestin Fig. 10. I-Ieretofore the sides of ribs such as the rib I! have been flat and have been connected to the body of the bar by a fillet of insignificant extent, the effort being to make the fillet as small as was commercially practicable. The theory was that the steep fiat side or the rib would prevent a wedging'efiect which would split the concrete. One step in the as illustrated in Fig. 10, the fillet isof such large radius that it extends all the way to the tip of the rib II. ,A satisfactory radius of curvature has been found to be one and a half times the height of the rib, which height is represented by the dimension h in Fig. 10. This radius is in the direction perpendicular to the hell: of the rib at a given point, and hence the curvature longitudinally of the bar is of slightly greater radius and incidentally the fillet probably does not have a true amuate curvature in this longitudinal section. A fillet having a-curvature of only half the dimension h, at least in the larger sizes, would probably enable the cement to have good contact with the metal. At least it has been found that a radius of curvature of .06 inch is suflicient in the smaller sizes, and so it probably would be in the larger sizes also.

Contrary to general belief heretofore, a fillet of large radius does not objectionably affect the reinforcing characteristics of the bar. In fact, it seems to improve these characteristics. There are two possible reasons for this which may be stated for such help as they may be in designing the variations of applicant's invention although applicant is not to be limited to them. First is the fact that the steepest part of applicant's rib is sufficiently steep so thatat that point it is within the angle of frictional repose between concrete and metal. According to one prior art publication, an inclination as low as 60 from the axis is permissible. The inclination of the rib l2 adjacent its tip is preferably in the neighborhood of 70 or more from the axis. If there is no slippage of the bar or portion thereof 'in the concrete, there will be no splitting. If thereis slippage, this outer portion of the rib will engage the concrete, at least as soon as any other portion of the rib, and will prevent any further slippage of the bar'such as would be necessary to produce a wedging and splitting action.

A theory which may account for the fact that the wide fillet seems to be actually better than the insignificant filletv of the prior art is that the concrete usually does not make contact with the bar in the vicinity of a sharp fillet, whereas with a fillet of large radius it will make intimate contact all along the fillet. The adhesion of the concrete or the cement therein to the steel of the bar is an important factor in preventing slippage. Furthermore, where there is such intimate contact, minute irregularities in the surface of the bar lligve the same interlocking effect as do the ribs Furthermore, it should be observed that the bar should be designed to have a substantial excess of bearing area in order to have adequate bearing area even when the concrete settles. when the concrete settles, it settles away from the shallow or wedge-like portion of the fillet but remains in contact or relatively close to the steep I Of course, theoretically, assuming that the space between the ribs is entirely filled with concrete,

have moved the length of the pocket 22.

the shearresistance of the concrete may be slightly decreased because more concrete is' dis- 3 placed by ribs than if fewer ribs are used. This can be partially offset by making the ribs thinner inasmuch as a large number of thin ribs will have as much bearing strength as a small number of thin ribs. Furthermore, it is probable that in the instances where the shearing strength approaches the limit of safety, namely,

i when there has been settling of the concrete,

the close spacing of the ribs does not in effect 7 decrease the shearing resistance nearly as much as has been heretofore supposed. When there has been settling of the concrete, the concrete does not necessarily shear along the theoretical line extending from the tip of one rib to the tip of the next. It may instead crumble or shear along a diagonal line since the settling has left a space into which the crumbling concrete can shift. Accordingly, it is possible that the close spacing of the ribs of the present invention does not in fact decrease the actual shear resistance of the concrete under the conditions most adverse to the shear resistance, but may increase it. The present spacing is believed to come close to the ideal for maximum shear resistance under adverse conditions.

One very definite advantage of the close spacing of the ribs in accordance with this invention is seen by comparing Figs. 8 and 9. These figures represent a vertically disposed reinforcing bar in concrete which has settled. In Fig. 8 a wider spacing of rib 2| is illustrated, and it will be observed that below each rib there is a pocket 22 formed by settlement of the concrete.

that the bar of the present invention with its closely spaced ribs is used. No pockets 22 adjacent the ribs l2 have been shown, since it is the distance which the rib will have. to shift in believed that such pockets, if they exist, are

negligible. If the ribs I2 are spaced apart only one-fifth as far as the ribs 2|, the settlement of the concrete occurring between the ribs will be only one-fifth as much. It is entirely possible, however, that the close spacing of the ribs,

together with the intimate contact obtained by j virtue of the large'radius fillets, prevents any settling of the concrete in contact with the bar from occurring. It will be realized that concrete is fairly fluid during its settling period. This being the case, a very small difference in adhesive force can make the difference between the concretes settling away from the ribs and adhesive force so that the flow necessary to settling occurs elsewhere. The larger number 'of ribs not only has more adhesive force, tending to cause the settling to occur elsewhere than in contact with the bars, but they also have better interlocking with the semifiuid concrete. The combination of the better interlocking and the increased adhesion is believed, under at least some circumstances, to prevent settling of the concrete in contact with the bar so that no pockets 22 are formed. However, even if some settling does occur, the close spacing is highly its being held in contact'with the ribs by the the concrete before it comes to rest at the bottom of the pocket. A very small reduction in the amount that the rib can shift may make the difference between satisfaction and complete failure. Furthermore, it should be observed that when the bar does slip in the concrete so that the adhesion between the concrete and the body portion of the bar is lost, a, large number of ribs is highly advantageous since they provide the more extensive bearing area which is necessary in the absence of adhesion.

Because of incorporating these various features simultaneously in the same bar, a bar is produced which is far superior to any bar heretofore known, particularly in that it will give much greater and more dependable reinforcing effect for a given weight of metal. This is partly the result of divising a bar in which the various features which have heretofore seemed irreconcilable could be incorporated, and this in turn has resulted partly from determining that large fillets were not objectionable and from a greater recognition of the importance of close spacing of the ribs. The determination that large fillets are not objectionable has made possible and commercially practical the formation of the close- 1y spaced ribs by deforming a smooth bar.

Although considerable, departures may be made from the preferred dimensions, it may be helpful to those utilizing the invention hereafter to set forth these preferred dimensions for a variety of sizes of bar, all dimensions being in inches.

, Lon nuditaa. was; .at .350 .200 .04 .05 /z .470 .250 .05 .06 .590 .285 .055 .075 .715 .285 .055 .075 V .840 .333 .06 .08 1 .955 .333 .065 .09 1% 1.075 .333 .075 .10 1% 1.190 .333 .075 .10

The thickness of the helical ribs is preferably quite small, from .02 inch in the smallest size to .04 inch in the largest. A size of .05 inch would still be much better than the prior art, and any improvement is desirable. The small size is epecially desirable where the spacing of the ribs is close.

It will be observed that the pitch angle (the angle of intersection of the helix of the ribs with a plane perpendicular to the axis) is about 10 in the largest size and about 18 in the smallest. It is preferred to keep the pitch angle below 20, although as high as 30", might prove to be satisfactory. Too steep a pitch might produce a twist- 7 ing force on the bar and other objectionable phenomena. Of course, the twisting force can be avoided by using crossing he1ixes,'but this is unnecessary with the low pitch'angles of the preferred form of the invention. Crossing helixes are somewhat undesirable.

Preferably, the various dimensions are so chosen that each bar will have a total cross-sectional areaequal to one-tenth of a square inch or a multiple thereof. This has an advantage in figuring the requirements, weights, etc. They can be given numbers corresponding to the crosssectional area in tenths of a square inch. Thenumber will then also inthcate the weight per linear yard, in pounds. I

The bars are often used in sets, with perhaps two different sizes cooperating in one structure. For this reason, as well as for ease and uniformity in calculations and requirements, it is desirable to have the whole line or set fit a simple formula with respect to bearing area necessary to utilize the full strength of the bar. The illustrated bars lend themselves to thisbecause in all the sizes given the ratio of projected bearing area available in a length equal to 15 diameters tothe cross section is fairly uniform, between and 13.

Projected bearing area means the projection of the ribs in a plane perpendicular to the axis of the bar. As a matter of fact, a length of diameters in any size, properly embedded in good concrete beyond the point of strain, will utilize the full useful strength of the bar.

Although bars having body portions of circular cross section are preferred, the invention may be used with bars of' square cross sections or any other shape.

I claim:

1. A concrete reinforcing bar including an elongated body portion and rib means projecting therefrom, characterized by the disposition of the rib means to extend along the bar at a pitchangle not greater than with a circumferential extent at least approximately 88% of the periphery of the bar, to extend uniformly along the length of each of two halves of the bar to provide a uniform cross-sectional area along each half of the bar and spaced apart along the length of the bar from center to center approximately V inch minus /4 the amount, if any, the diameter of the body portion is less than inch, andeby the shaping of the rib means with a thickness approximately .02 to .04 inch and fillets connecting the rib means to the body portion having a radius of curvature transversely of the ribs of approximately 1 and times the meter of the body is-less than 1; inch and by. the shaping of the rib means with a minimum thickness approximately .02 to .04 inch and fillets connecting the rib means to the body portion having a radius of curvature transversely of the ribs of approximately 1% times the height of the rib means.

4. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally heiically with a pitch-angle not greater than 20, extending uniformly along the length of the bar to provide a uniform crosssectional area along the bar, and spaced apart along the length of one side of the bar at intervals at least as small as 56 inch, and. by the shaping of the rib means with a minimum thickness approximately .02 to .04 inch and fillets connecting the ri means to the body portion having a radius 0 curvature transversely of the ribs of approximately 1 times the height of the rib means.

5. A concrete reinforcing bar including an elongate body portion and .rib means projecting height of the rib means, and further character ized by additional ribs extending longitudinally of the bar, separating the two halves, and having a thickness less than approximately 15% of the thickness of the body portion.

2. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means to extend along the bar at a pitchangle not greater than 30, to extend uniformly along the length of each of two halves of the bar to provide a uniform cross-sectional area along each half of the bar and spaced apart along the length of the bar from center to center at least.

as close as approximately V2 inch, and by the shaping of the rib means with a minimum thickness approximately .02 to .04 inch and fillets connecting the rib means to the body portion having a radius of curvature transversely of the ribs of approximately 1 times the height of the rib means, and further characterized by additional ribs extending longitudinally of the bar and separating the two halves.

3. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means to extend along the bar at a pitchangle not greater than 30, to extend uniformly along the length of each of two halves of the bar to provide a uniform cross-sectional area along each half of the bar and spaced apart along the length of the bar from center to center approximately ,6 inch minus V4 the amount the ditherefrom, characterized by the disposition of; the rib means generally heiically with a pitch-, angle not greater than 20, extending uniformly along the length of the bar to provide axuniform cross-sectional area along the bar, and spaced apart along the length of one side of the bar at intervals at least as small as inch, and by the shaping of the rib means with fillets connecting the rib means to the body portion having a radius of curvature transversely of the ribs of approximately 1 /2 times the height of the rib means.

6. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally heiically with a pitch-angle not greater than 20, extending uniformly along the length of the bar to rovide a uniform crosssectional area along the bar, and by the shaping of the rib means with fillets connecting the helical ly extending rib means to the body portion having a radius of curvature transversely of the ribs of approximately 1 times the height of the rib means.

7. A concrete reinforcing bar including an elongate body portion generally circular in cross section, and rib means projecting therefrom; characterized by the disposition of the rib means generally heiically with a pitch-angle not greater than 20, extending uniformly along the length of 8. A concrete reinforcing bar including an elongate body portion generally circular in cross section, and rib means projecting therefrom, characterized by the disposition of the rib means generally heiically with a pitch-angle not greater than 20, extending uniformly along the length of the bar to provide a substantially uniform cross-sectional area along the bar, and spaced apart along the length of one side of the bar at intervals at least as small as ,5 inch, and by the shaping of the rib means with a minimum thickness approximately .02 to .04 inch and fillets connecting the rib means to the body portion'having a radius of curvature transversely of the ribs of approximately 1% times the height of the rib means.

9. A concrete reinforcing bar including an by the shaping of the rib means wtih fillets connecting the transversely extending rib means to g the body portion having an outwardly concave radius of curvature longitudinally of the bar. equal to at least approximately half the height of the rib means.

10. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar, and by the shaping of the rib means with fillets connecting the transversely extending rib means to the body portion having an outwardly concave radius of curvature longitudinally of the bar equal to at least approximately half the height of the rib means.

11. A concrete reinforcing bar including an elongate body portion deformed to provide rib means projecting therefrom, characterized by the disposition of the rib means to extend generally transversely of the length of the bar at least approximately 88% of the periphery of the bar, and spaced apart along the length of the bar at intervals not over /2 inch, and by the shaping of the rib means substantially wider at the base thereof than at the tip, with a portion of one face sloping outward at an angle of at least approximately 70 from the length of the bar.

12. A concrete reinforcing bar including an elongate body portion generally circular in cross section and deformed to provide rib means projecting therefrom, characterized by the disposition of the rib means to extend generally transversely of the length of the bar at least approximately 88% of the periphery of the bar, and spaced apart along the length of the bar at in- .tervals not over inch, and by the shaping of the rib means substantially wider at the base thereof than at the tip, with a portion of one face sloping outward at an angle of at least approximately 70 from the length of the bar.

L3. A concrete reinforcing bar including an elongate body portion generally circularin cross section and deformed to provide rib means projecting therefrom, characterized by the disposition of the rib means to extend generally transversely of the length of the bar with a minimum thickness not over approximately .05 inch, and spaced apart along the length of the bar at intervals not over /2 inch, and by the shaping of the rib means substantially wider at the base thereof than at the tip, with a portion of one face sloping outward at an angle of at least approximately 70 from the length of the bar.

1 14. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and at an angle of at least '70 degrees with respect thereto, and by the shaping of the rib means with fillets along said transversely extending rib means connecting the rib means to the body portion having a radius of curvature longitudinally of the bar equal to approximately one and one-half times the height of the rib means.

15. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and by at least suflicient decrease of steepness of at least the lower portion of the faces of the transverse rib means to form fillets connecting the surfaces of the transversely extending rib means therebeyond to the body portion having an outwardly concave radius of'curvature longitudinally of the bar equal to at least aproximately'half the height of the rib means.

16. A concrete reinforcing bar including an elongate body portion and rib means projectin therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and by at least sufiicient decrease of steepness of at least the-lower portion of the faces of the transverse rib means to-form fillets connecting the surfaces of the transversely extending rib means therebeyond to the body portion having an outwardly concave radius of ourvature longitudinally of the bar equal to at least approximately half the height of the rib means and at least .06 inch.

1'7. A rolled steel bar for reinforcing concrete including an elongate body portion deformed to provide rib means including oppositelongitudinal ribs, and transverse ribs extending between them, disposed to extend at an angle of at least 60 from the length of the bar, having a substantial height throughout at least 88% of the periphery of the bar and having their centers spaced along the length of the bar at intervals not over onehalf the spacing of the turns of a 30 helix along the bar, the faces of said transverse ribs being at least as steep adjacent the tips of the ribs as at any other portion of the rib, the'thickness of the rib in cross section increasing toward the body of the bar at least enough to form a fillet connecting the body portion to a continuation of the slope of the face adjacent the tip and having a radius of at least one-half the height of the rib and at least .06 inch, and the space between the ribs at their tips being several times the thickness of a rib at its tip.

18. A rolled steel bar for reinforcing concrete including an elongate body portion deformed to provide rib means including opposite longitudinal ribs, and transverse ribs extending between them, disposed to extend at an angle of at least 60 from the length of the bar, having a substantial height through at least 88% of the periphery of the bar and having their centers spaced along the length of the bar at intervals not over onehalf the spacing of the turns of a 30 helix along the bar, the faces of said transverse ribs being at least as steep adjacent the tips of the ribs as at any other portion of the rib and having an inclination at least as steep as 60 from the axis of the bar, the thickness of the rib in cross section increasing toward the body of the bar at least enough to form a fillet connecting the body portion to a continuation of the slope of the face adjacent the tip and having a radius of at least one-half the height of the rib and at least .06 inch, and the space between the ribs at their tips being several times the thickness of a rib at its tip.

19. A rolled steel bar for reinforcing concrete including an elongate body pOrtion deformed to provide rib means including opposite longitudinal ribs, and transverse ribs extending between them disposed to extend at an angle of at least 60 1 from the length of the bar, having a substantial height all of the way from one longitudinal rib to another and having their centers spaced along the length of the bar at intervals not over onehalf the spacing of the turns of a 30 helix along the bar, the faces of said transverse ribs being at least as steep adjacent the tips of the ribs as at any other portion of the rib and having an inclination at least as steep as 60 from the axis of the bar, the thickness of the rib in cross section increasing toward the body of the bar at least enough to form a fillet connecting the body portion to a continuation of the slope of the face adjacent the tip and having a radius of at least one-half the height of the rib and at least .06 inch; the space between the ribs at their tips being several times the thickness of a rib at its tip.

20. A rolled steel bar for reinforcing concrete including an elongate body portion deformed to provide rib means including opposite longitudinal ribs, and transverse ribs extending between them, disposed to extend at an angle of at least 60 from the length of the bar, having a substantial height throughout at least 88% of the periphery -of the bar and having their centers spaced along the length of the bar at intervals not over onehalf the space of the turns of a 30 helix along the bar, the faces of said transverse ribs being at least as steep adjacent the tips of the ribs as at any other portion of the rib and progressively decreasing in steepness inwardly at least along the inner half of the rib, and the space between the ribs at their tips being several times the thickness of a rib at its tip.

21. A rolled steel bar forireinforcing concrete including an elongate body portion deformed to provide rib means including opposite longitudinal ribs, and transverse ribs extending between them disposed to extend at an angle of at least 60 from the length of the bar, having a substantial height all of the way from one longitudinal rib to another and having their centers spaced along the length of the bar at intervals not over one-half the spacing of the turns of a 30 helix along the bar, the faces of said transverse ribs being at least as steep adjacent the tips Of the ribs as at any other portion of the rib and progressively decreasing in, steepness inwardly at least along the inner half of the rib, and the space between the ribs at their tips being several times the thickness of a rib at its tip.

22. A rolled steel bar for reinforcing concrete including an elongate body portion deformed to provide rib means including transverse ribs disposed to extend at an angle of at least 60 from the length of the bar, having a substantial height and having their centers spaced along the length of the bar at intervals not over one-half the spacing of the turns of a 30 helix along the bar, the faces of said transverse ribs including portions along the outer third of the faces at least as steep elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and by a shaping of the faces of the ribs with a continuously decreasing steepness substantially from the tops of the ribs to the body.

24. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and by a shaping of the faces of the ribs with less steepness along the inner portion of the rib, extending from the body to at least half the height of the rib, than along the outer part of the rib.

25. A concrete reinforcing bar including an elongate body portion and rib means projecting therefrom, characterized by the disposition of the rib means generally transversely of the length of the bar and by a shaping of the faces of the ribs with less steepness along the portion of the rib, extending from the body almost to the tip of the rib, than immediately adjacent the tip of the rib.

CARL A. MENZEL. 

